The Histotechnology Core requested provides access to all investigators in this program-project grant to histotechnology services and diagnostic services for tissues obtained from rodents. Currently available support services of this type are working at overload capacity .with only two histotechnologists and several undergraduate student assistants. They are presently servicing 18 faculty members, which in the last year produced more than 80,000 slides of a variety of types. The single experienced histotechnologist requested will work on projects for members of this program-project grant, providing not only routine but a variety of specialized histotechnology methods on both fixed and frozen tissue samples, including enzyme histochemistry, immunohistochemistry, and autoradiography. It is anticipated that this individual will also be trained in in situ hybridization, a technique presently not available to these projects. This technology will be essential to several projects in the program-project grant. Histopathologic interpretation will be provided by the Core director as needed by members of this grant.